1. Field of the Invention
The present invention pertains to measurement of multiphase fluid (liquid and gas) flow using one or more densitometers, a pump, flow restriction or heat exchanger to effect a change in pressure and temperature of the fluid flow and pressure and temperature sensors for measuring the flowstream both upstream and downstream of the restriction, pump or heat exchanger.
2. Background
Various methods have been developed for measuring multiphase fluid flow where widely varying ratios of gas to liquid are experienced and wherein a high degree of measurement accuracy may or may not be important. U.S. patent application Ser. No. 08/131,813, filed Oct. 5, 1993, and U.S. patent application Ser. No. 08/179,411, filed Jan. 10, 1994, both by M. M. Kolpak and both assigned to the assignee of the present invention, describe various types of flowmeters for measuring multiphase fluid flow, particularly mixtures of oil, water and gas which result from the production of hydrocarbons from subterranean wells. U.S. Pat. No. 5,099,697, issued Mar. 31, 1992 to J. Agar, also describes a multiphase fluid flow measurement system adapted to measure flows of oil, water and gas.
However, there has been a continuing need to develop flow measurement systems and methods which may be easily adapted to existing flow lines leading from subterranean wells, flow lines leading to or from separation devices for separating gas from liquid and similar applications where a high degree of accuracy is not required, where a relatively high percentage of the flow is gas and wherein minimal interruption of the fluid flow system is required or is desirable.
Many types of known flowmeter systems do not perform well where a high gas-to-liquid ratio or gas fraction of the total volumetric flow exists or wherein a substantial number of fluid parameters, including fluid density, must be premeasured or otherwise known in order to perform the measurement method. The devices and methods described herein overcome some of the deficiencies of existing multiphase fluid flow measurement systems and methods.